title: Molecular architecture of the ankyrin SOCS box family of Cul5-dependent E3 ubiquitin ligases.
abstract: Multi-subunit Cullin-RING E3 ligases often use repeat domain proteins as substrate-specific adaptors. Structures of these macromolecular assemblies are determined for the F-box-containing leucine-rich repeat and WD40 repeat families, but not for the suppressor of cytokine signaling (SOCS)-box-containing ankyrin repeat proteins (ASB1-18), which assemble with Elongins B and C and Cul5. We determined the crystal structures of the ternary complex of ASB9-Elongin B/C as well as the interacting N-terminal domain of Cul5 and used structural comparisons to establish a model for the complete Cul5-based E3 ligase. The structures reveal a distinct architecture of the ASB9 complex that positions the ankyrin domain coaxial to the SOCS box-Elongin B/C complex and perpendicular to other repeat protein complexes. This alternative architecture appears favorable to present the ankyrin domain substrate-binding site to the E2-ubiquitin, while also providing spacing suitable for bulky ASB9 substrates, such as the creatine kinases. The presented Cul5 structure also differs from previous models and deviates from other Cullins via a rigid-body rotation between Cullin repeats. This work highlights the adaptability of repeat domain proteins as scaffolds in substrate recognition and lays the foundation for future structure-function studies of this important E3 family.
authors.affiliation: Structural Genomics Consortium, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, United Kingdom.
authors.forename: João R C
authors.initials: JR
authors.lastname: Muniz
authors.forename: Kunde
authors.initials: K
authors.lastname: Guo
authors.forename: Nadia J
authors.initials: NJ
authors.lastname: Kershaw
authors.forename: Vikram
authors.initials: V
authors.lastname: Ayinampudi
authors.forename: Frank
authors.initials: F
authors.lastname: von Delft
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Babon
authors.forename: Alex N
authors.initials: AN
authors.lastname: Bullock
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017487:Ankyrins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D044842:Cullin Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D016415:Sequence Alignment; D050826:Suppressor of Cytokine Signaling Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D017487:Ankyrins; D044842:Cullin Proteins; D050826:Suppressor of Cytokine Signaling Proteins; D044767:Ubiquitin-Protein Ligases
keywords: ASB; C-terminal domain; CTD; N-terminal domain; NTD; PDB; Protein Data Bank; SCF; SOCS; Skp1–Cul1–F-box; ankyrin SOCS box; degradation; proteasome; protein–protein interaction; signaling; suppressor of cytokine signaling; ubiquitination